I’d rather the sky wasn’t filled with planes following replays that don’t react to anyone or basic rules of flying which is what the current third pastry add-ons allow. If that was the system from Asobo then I’d be very unhappy, and so would many others I suspect. For example you come in to land and a plane (in replay mode) keeps going backwards and forwards on the runway causing you to have to go around time and time again. Fun.
A proper replay system needs to be developed which is what Asobo are doing. And I know it’s not straight forward and am happy to wait until they can get it right.
Replaying a flight needs to be kept separate from those on live flights.
There’s no replay system I’ve ever seen that takes place during the current game. It’s always something you view afterwards.
As for other games with replays I think you’d be looking at things like racing games like Forza. I don’t know of any open world types though, mainly I think as they tend to be sandbox and you don’t care that much what happens in them.